Purpose: To utilize standardized procedures to measure the immune response in clinical trials of acellular pertussis vaccine (ACPV). 1. NIAID - Multicenter Phase II Trial: The Laboratory of Pertussis served as the serologic reference laboratory for the multicenter trial of 13 candidate ACPVs. Four ELISA assays (IgG-PT, IgG-FHA, IgG-69k, IgG fimbriae) and whole-cell agglutinins were performed on over 4000 sera for this study (more than 25,000 individual assay results were reported; of these, approximately 1500 were performed in FY92). As part of the study, FDA methodology and reagents were transferred to the NIAID-supported lab which performed confirmatory testing on a 10 percent sub-sample of sera from the study and to the lab which performed the CHO-cell testing. (a) FDA scientists advised NIAID statisticians on the procedures for analysing and presenting the serologic data from the NIAID multicenter trial. (b) Quality assurance analyses of the FDA serologic data demonstrated a high reproducibility and consistency of the data generated in the FDA lab and demonstrated a high degree of correlation among the results obtained in the 3 testing laboratories. (c) FDA scientists analysed and presented the serologic data from the trial. (d) Analysis of the data demonstrated a good correlation between IgG anti-PT and CHO-cell titers for children immunized with any of the whole-cell or acellular vaccines. (e) Analysis of the data demonstrated a good correltation between IgA anti-fimbriae antibodies and agglutinin titers for children immunized with any whole-cell or acellular vaccine containing fimbriae. 2. The 4 ELISA assays were performed on sera from approximately 80 Japanese children immunized with either the Biken or Takeda acellular vaccines. These results will be compared to responses in U.S. children immunized with vaccines from the same manufacturer. 3. Development of new assays. Procedures are being developed to measure epitope specific responses in individuals immunized with acellular vaccines.